Wool scouring



Patented May 15, 1951 WOOL SCOURING Archie Louis Dubeau, Rumford, R. I., assignor to Mathieson Chemical Corporation, a corporation of Virginia N Drawing. Application March 27, 1946, Serial No. 657,626

2 Claims.

This invention relates to improvements in the scouring of wool including both shorn wool and pulled wool.

In accordance with conventional practice, wool before utilization in the production of yarn is subjected to treatment in a series or train of five treating vessels known as bowls. In the first bowl of the train, the wool is deswinted by washing with cold water. In the 2nd and 3rd bowls, the deswinted wool is scoured, usually at a temperature of about 125 F., with an aqueous solution of soap and sodium carbonate. The 4th and 5th bowls are essentially rinsing bowls, but the last bowl, from which the wool is passed to a dryer, may contain a bleaching agent, conventionally hydrogen peroxide.

The scouring in the No. 2 and No. 3 bowls, when the system does not include mechanical grease recovery equipment, proceeds with periodic removal of part of the solution and replacement of the removed portion with warm water, fresh soda ash and soap being added to maintain the solution at the desired chemical. concentration. Soda ash and soap are also continuously or intermittently added during the periods between the half dumps. At the end of 24 .hours, the bowls are usually completely emptied, thoroughly washed and charged with fresh liquor.

Where continuous grease recovery equipment is employed, the scouring solution is circulated through the wool and through the grease machine, the solution ordinarily being caused to flow from the No. 3 to the No. 2 bowl, through the grease machine and then back to the No. 3 bowl. Some operators, however, prefer to recover the grease from the No. 2 bowl only, in which case the scouring liquor is withdrawn from the wool exit end of the No. 2 bowl, passed through the grease machine, then returned to the No. 2 bowl at the wool entering end of the bowl.

I have discovered in the scouring of shorn wool, by the method described, that the sodium carbonate in a considerable amount is converted to sodium bicarbonate and that additional quantities of sodium bicarbonate are formed in some other way, possibly from carbon dioxide in the air or from some carbon dioxidecontaining compound in the wool. I have further discovered that the presence of sodium bicarbonate in the scouring liquor is essential to proper scouring. But the discovery on which my invention as applied to shorn wool is more directly founded is that the ratio of sodium car- 2 bonate to sodium bicarbonate in the scouring liquor is critical from the standpoint of optimum scouring action.

In the scouring of a lime-pulled wool or a grease wool containing alkali by the conventional method, sodium bicarbonate does not appear to be formed, at least to any substantial extent. My invention, insofar as such alkaline wools is concerned, is based on the discoverey that through the conjoint use of sodium carbonate and sodium bicarbonate greatly improved scouring may be achieved.

If during the scouring of shorn wool, by the prior art process, a sample of the scouring liquor is taken from the first bowl, in which about 90% of the scouring is accomplished, before each addition of soda ash, and a double titration with .09 normal HCl run on the samples using phenolphthalein as the indicator in the first titration and methyl orange as the indicator in the second, it will be found that the spread between. the phenophthalein end point and the methyl orange end point (total alkalinity) in terms of cubic centimeters of acid becomes progressively greater. This means that the proportion of bicarbonate in the liquor progressively increases during the scouring, albeit a part of the total alkalinity may be due to the presence of compounds other than sodium carbonate and sodium bicarbonate.

The accompanying Table I, submitted in illustration of the immediate foregoing, is based on an operation in which the wool was treated at the rate of about 1000 pounds per hour. The liquor in the No. 2 bowl consisted initially of 3500 gallons of water, 120 gallons of soda ash solution containing 92.5 pounds of soda ash, and 30 gallons of soap solution containing 8.3 pounds of soap, while the liquor in the No. 3 bowl at the beginning of the operation consisted of 1500 gallons of water, gallons of soda ash solution containing 46.25 pounds of soda ash, and 30 gallons of soap solution having a soap concentration of 0.277 pound per gallon. As the scouring proceeded, the liquor was fortified every 45 minutes by adding 36 gallons of soda ash solution containing 27.8 pounds of soda ash to the No. 2 bowl and by adding 18 gallons of soda ash solution containing 13.9 pounds of soda ash together with 12 gallons of soap solution containing 3.33 pounds of soap to the No. 3 bowl. At the end of each six hour period, half of the scouring solution was withdrawn from both scouring bowls and the withdrawn solution replaced with water. Following each addition of make-up water, 90 gallons of soda ash solution containing 69.5 pounds of soda ash and 30 gallons of soap solution containing 0.277 pound of soap per gallon were added to the No. 2 bowl, and 45 gallons of soda ash solution containing 34.6 pounds of soda ash and 30 gallons of soap solution were added to the No. 3 bowl.

i centration of bicarbonate is negligible, in fact, it is advantageous in preparing the initial solution to add bicarbonate.

In the case of pulled wool where sodium bicarbonate is not formed as an incident of the scouring, the wool being alkaline from pre-treatment' with lime, the desired composition of the Table I Total c c s C. c.s .09 normal H01 3 Alkalinity Calculated il g' i Sample No. to Phenolph- Math 1 as Carbonate. thalein End a g N21100:, and NaHOOa Bicarbonat Pmnt End Point 2 5.3 2.12 1-09 110.51 1.9 6.9 2.01 2.6 V 11.29 2. 3 8.6 2. 44 3.36 1:1. 39 2. 3 10. a 2. 44 s. 04 112. 06 2. 4 13.1 2. 54 7.17 1:2. 82 2. 9 14. 6 3. 07 7. 59 112. 47 2. 9 16.1 3. 07 8.65 1:2. 82 2. 7 16.7 2.86 9.49 1:3.32 2. 4 17.3 2. 54 1o. 114.13

Thesamples in the table were taken immediately before each addition of soda ash and soap. Although the total alkalinity is calculated as due entirely to sodium carbonate and bicarbonate, it is to be understood that a relatively small part of the alkalinity may derive from other compounds formed during the scouring having a pI-I value similar to that of sodium bicarbonate. Alkalinity as sodium carbonate is calculated by multiplying the cubic centimeters of acid to the phenolphthalein end point by 1.06; alkalinity as sodium bicarbonate by subtracting twice the cubic centimeters of acid to the phenolphthalein end point from the cubic centimeters of acid to the methyl orange end point and multiplying the difference by 0.84. The table shows that in the conventional process, in which no effort is made to control the carbonatezbicarbonate' ratio, the weight of bicarbonate present in the solution soon exceeds twice the weight of carbonate present.

In accordance with the present invention, I so control the composition of the scouring liquor that the ratio of the figure obtained by multiplying the cubic centimeters of 0.9 normal HCl re-. quired to reach the phenolphthalein end point by 1.06 to the figure obtained by multiplying the difference between twice the cubic centimeters of .09 normal I-ICl to phenolphthalein end point and the cubic centimeters of .09 normal HCl required to reach the methyl orange end point by 0.84 is kept substantially at all times within the range of about 120.5 to 1:2. Optimum results appear to be obtained at a ratio of about 1:1. It will be understood that the apparent carbonate: bicarbonate ratio referred to in the appended claims is determined as just noted.

In the scouring of shorn or other acidic wools, the composition of the scouring liquor can be maintained within the prescribed limits, with advantage. through the continuous or intermittent introduction of controlled amounts of aqueous caustic soda. Less preferably, aqueous caustic potash or an aqueous solution of an alkaline earth metal hydroxide, such as calcium-hydroxide may be introduced into the liquor. The added alkali, it will'be understood, acts to convert excess bicarbonate back to carbonate in accordance with the equation:

The alkaline solution is not, of course, added from the very begining of the scouring when thepconscouring liquor is maintained in accordance with my invention by the continuous or intermittent addition of sodium bicarbonate or an acid or acid salt, such as acid phosphate. The initial solution in the instance of alkaline wools should be made up to contain bicarbonate in an amount indicated by the limits above.

In a preferred embodiment of my invention as aplied to acid wool, the caustic solution is added to the first scouring bowl only, and in the company of liquor removed from the bowl rather than directly to the bowl. The caustic may become completely reacted before it enters the bowl. Direct addition of the caustic solution to the bowl appears disadvantageous as resulting in localized harshening of the wool. The liquor to which the caustic solution is to be added is preferably withdrawn from the wool exit end of the bowl, passed through a trough or tank where the caustic solution is charged to the liquor, and the adjusted liquor pumped back into the woolentering end of the bowl. The caustic solution most suitably has a NaOI-I concentration of about 1.5 pounds per gallon. Where the caustic is added continuously, which is preferable in most cases, a variable feed proportioning pump may be employed with advantage. The rate at which the causic solution is added is determined, as provicusly indicated, by the rate of bicarbonate formation.

The practice of my invention is further illustrated by the following examples:

EXAMPLE 1 The Wool was fed to the system at the rate of about 1200 pounds per hour. The caustic solution used consisted of about 20 pounds sodium hydroxide in 50 gallons of water. The solution was continuously added to liquor from the first scouringbowl only, and at a rate equivalent to 3.5 pounds of NaOH per thousand pounds or wool. The data on this run and the data on a second run, similarly conducted, are given in accompanying Tables II and III:

Table II C. c.s .09 C. c.s .09 Apparent sample normal HCl norml HCl Alkalinity Calculated atio Time NO to end point to end point as Carbonate:

' Phenolph- Methyl NaeCOs and NaHOO; Bicarbonalein Orange ate Table III C. c.s .09 O. c.s .09 Apparent Sam 19 normal H Cl norml H01 Alkalinity Calculated Ratio Tune to end pomt to end point as Carbonate:

' Phenolph- Methyl NazCOz and NaHGOa Bicarbonthalein Orange ate 9.30.... l 3.7 11.3 3. 92 3. 28 1: .83 10.00.. 2 3.9 12.6 4.13 4.05 1: .95 10.30.. 3 4.1 13.2 4. 4. 2 l: .96 11.00.. 4 4. 7 13. 9 4. 98 3. 78 1: .75 11.30.. 5 3. 9 13.1 4.13 4. 45 1:1. 07 12.00.. 6 4. 3 13.3 4. 56 3. 85 l: .84 12.30.. 7 4. 0 13.3 4. 24 4. 45 1:1. 05 1.00.... 8 4.0 13.4 4. 24 4. 53 1:1. 06 1.30...- 9 3. 8 13.0 4.02 4. 53 1:1. 12 2.00.... 10 3. 4 12. 8 3. 60 5.04 1:1. 4 2.30.... 11 3. 4 12.8 3. 60 5. 04 1:1. 4

EXAMPLE 2 I elalmz In this instance, pulled wool was treated at the rate of 700 pounds per hour using conventional bowls. The scouring was carried out at a temperature of 130 F. and the make-up on the scouring bowls was as follows:

Water --gallons-- 3,750 Sodium bicarbonate --pounds- 300 Sodium carbonate --do---- 180 Soap --do 12 During the course of the run, 100 pounds additional of sodium bicarbonate was added to the first scouring bowl in increments of about 16 pounds. Data on the run is given in the following table:

Table IV Ratio Car- Per Cent Per Cent Time H bonatezB1- P M2003 Nance: carbonate 1. The process of securing wool which comprises continuously passing wool to be scoured in contact with a bath of aqueous scouring solution comprising soda ash, sodium bicarbonate and soap and maintaining the apparent carbonatezbicarbonate ratio of the bath within the range of 1:05 to 1:2 by adding to the solution of the bath predetermined amounts of the hydroxide of a metal of the group consisting of the alkali metals and the alkaline earth metals in aqueous solution.

2. The process of securing wool which comprises continuously passing wool to be scoured in contact with a bath of aqueous scouring solution comprising soda ash, sodium bicarbonate and soap and maintaining the apparent carbonatezbicarbcnate ratio of the bath within the range of 1:0.5 to 1:2 by continuously adding to the solution of the bath sodium hydroxide in aqueous solution.

ARCHIE LOUIS DUBEAU.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,183,142 Mackenzie Dec. 12, 1939 2,481,205 Dubeau Sept. 6, 1949 OTHER REFERENCES The Effect of Temperature in scouring Wool, by Le Compte and Creely in American DyestuiT Reporter, September 14, 1942, pages 453-455.

Washing, Cleaning, and Polishing Materials, National Bureau of Standards Circular C424, 1939, pages 2324.

The Chemistry of Laundry Materials, by D. N. Jackman, 1931, pages 44-47. 

1. THE PROCESS OF SCOURING WOOL WHICH COMPRISES CONTINUOUSLY PASSING WOOL TO BE SCOURED IN CONTACT WITH A BATH OF AQUEOUS SCOURING SOLUTION COMPRISING SODA ASH, SODIUM BICARBONATE AND SOAP AND MAINTAINING THE APPARENT CARBONATE: BICARBONATE RATIO OF THE BATH WITHIN THE RANGE OF 1:0.5 TO 1:2 BY ADDING TO THE SOLUTION OF THE BATH PREDETERMINED AMOUNTS OF THE HYDROXIDE OF A METAL OF THE GROUP CONSISTING OF THE ALKALI METALS AND THE ALKALINE EARTH METALS IN AQUEOUS SOLUTION. 